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WORK ENERGY POWER (Assignment-1)

*Q1*. A water pump lifts water from a level 10 m below the ground. Water is pumped at a rate of 30

kg/minute with negligible velocity. Calculate the minimum horse power the engine should have to

do this?

Answer: 6.6 × 10⁻² hp

*Q2*. A man weighs 60 kg. Calculate work done by gravity as he climbs a ladder of heights 5m.

Answer: -2940 J

*Q3*. A body of mass 0.3 kg is taken up an inclined plane of length 10 m and height 5 m, and then allowed

to slide down to the bottom again. The coefficient of friction between the body and the plane is 0.15

What is the

(a) Work done by the gravitational force over the round trip?

(b) Work done by the applied force on the upward journey?

(c) Work done by the frictional force over the round trip

(d) Kinetic energy of the body at the end of the trip?

Answer: zero, 18.5 J, -7.6J, 10.9J

*Q4*. A pump can throw up 10 quintals of coal per hour from a coal mine 120 m deep. Calculate the power of the engine in watt assuming that efficiency is 80%.

Answer: 408.3 watt